An auto document feeder (hereinafter referred to as an ADF) of an image scanning apparatus takes out an original document one by one, and conveys it to a reading portion of the image scanning apparatus. The ADF is provided with a conveying path having a gap necessary for the original document to be conveyed to the reading portion. When the gap is excessively wide, the reading accuracy of the original document becomes worse, and when the gap is excessively narrow, the original document gets jammed. Thus, it is important to ensure a suitable gap.
The gap between a conveying guide member of the ADF and the reading portion is adjusted by adjusting the height of the conveying guide member. In a related art image scanning apparatus, the operation of adjusting the height of the conveying guide member is performed while looking into the gap between the conveying guide member and the reading portion from the side, and therefore, the workability is bad.
In this point, JP-A-2007-189637 discloses a technique in which a recess for visual recognition of a gap between a conveying guide member of an ADF and a reading portion is provided in a main body cover of an image scanning apparatus incorporated in an image forming apparatus.
However, also in this technique, the operator must look into and confirm a gap of the reading portion of the ADF from the side, and there is a problem that the workability is bad.